Animal Experimental Study Of The Degradable Cage

Objective:The degradable material has been gradually developed and applied in clinical treatment as a new kind of biomaterial in recent years. The material itself has many advantages such as good compatibility, biodegradability。Its property such as molecular weight can be manipulated in composing process. This study is to develop a new cage made of degradable material (PDLLA), and put it into animal experiment to observe its influence on the fusion process and its transformation during degrading period. Biomechanical test is used to examine its change at different fusion time. This study is focus on the animal experiment, which will offer basic information for its further development and clinical application. Method: ①To design the cage made of degradable material by consulting relative domestic and overseas literatures in recent years.②To find out its influence of on bone fusion at different phase by histology ,electronic microscope compared with normal interbody fusion.③To reveal the degrading process of the material in spine fusion by gross observation , electronic microscope compared with normal interbody fusion.④To examine the biomechanical changes of the spine at different time of fusion process by biomechanical test.Result: ①The cage was successfully made which was cubic type and made of 80*104 molecular weight PDLLA degradable material.②The bone growth was not influenced in the early and medium period of fusion. While in the late stage, the bone fusion in the degraded part slowed down because of the existence of the material and the the increasing debris during degradation which result in the gradual calcification of the fibril and cartilage around the cage. The spine fusion was achieved in the end.③The degrading rate was non-lineal. In the early stage of fusion, the main degradation focus on the superficial decomposition and decrease of molecular weight. With the proceeding of fusion and degradation, the hydrolyzation speeding up and internal decomposition by self-catalyse result in the collapse and total disassemble of the material.④The strength of the material itself is higher than vertebra and the early result of the biomechanical test showed that the experimental group present higher strength and twisting than the compared group. With thebiomechanical changing of the material during degradation, the result gradually come close to the compared group in late stages.Conclusion: The degradable material PDLLA has good tissue compatibility and will not result in evident immune reaction. It has no obvious negative influence on fusion process and can be absorbed by tissue around it where new bone was formed and gradually replace the material even the speed of degradation was slower than that of bone growth in late stage. The PDLLA cage maintained its shape in the early time. Its biomechanical strength decreased in the late stage but was still enough to keep the structure from collapsing until fusion was achieved in the bone implant area and finally collapsed and gradually degraded after that. So it is concluded that PDLLA is a good kind of material with nice tissue compatibility which will satisfy the requirement of vertebra fusion. Improvement of its degradation in the late fusion stage and its bone-growth ability will accelerate its application in clinical treatment.